Comparative characteristics of screw terminals and traditional cable terminals

Over the past 5-6 years, along with traditional cable ends and crimp sleeves, a new group of products for fasteners and cable connections has appeared on the Russian electricity market — the so-called "bolt" (they are "screw", they are "mechanical"). , tops and sleeves.

Unlike soldering, this is an irrevocable thing of the past and traditionally a method of crimping, (using special crimping pliers, forming dies and punches) is based on fasteners "bolt" connectors on the clamp of the cable core with bolts (screws) with shear heads . When the calculated clamping force is reached, the head of the bolt breaks off, making the fixation irreversible, and the rest of the ferrule / bushing «body» of the bolt provides mechanical and electrical strength contact with the cable core. In a certain sense, the success of popularizing "bolt" connectors on the Russian market can be called paradoxical.

It first appeared a year before the '98 default.as part of the components of heat-shrinkable connectors «Raichem», abroad «mechanical miracle «at a price of $ 20 per piece practically had no chance of national recognition.

Craftsmen were not late and after a short time the first domestic variations of the "bolt" found their wealthy and very rare buyers. Perhaps the only place of focus for overpriced “bolt” tips and bushings in those days was Mosenergo emergency repair service warehouses ...

Then there was a "default" ... Then there were scandalous rumors that «bolt» connectors burn like candles «that» the contact is formed bolt tightening is not as reliable as when fixing by crimping «this «bolt» will most likely be banned for use at all «…

As you know, however, there is no bad PR ... the "motor" that set the pace for the advancement of "bolt" connectors was the growing Russian heat shrink industry. Exactly the principle heat-shrink sleeve designed for the range of installed cable cross-sections to be used as components lugs and sleeves covering a similar range. In a situation where the needs of the end-user are uncertain (such as in the case of emergency repair services), or the end-user himself is unknown (resale chain), a complete set of heat-shrink sleeve cable lugs and connecting sleeves with symmetrical range seemed practical, convenient and appropriate.

In addition to the clear considerations of practicality and convenience, often relegating issues of price and quality to the background, the successful progress of «bolt» connectors has always been accompanied by a kind of train of elitism and caste superiority ... — assembly of heat-shrinkable sleeves with ears and sleeves with cutting heads — it's « cool, high quality, modern ... «

All these factors are driving the growth of bolt eye production.
Manufacturers finally began to give tips and sleeves with shear bolts more attention to the quality of the production of key bolt components tips and sleeves — the bolts themselves, because it is from the geometry of the bolt that the final quality and reliability of the connection between the sleeve and the tip depends on the cable under tension and as a result performance and reliability (not failure rate) of cable networks as a whole. They also became more active studies are carried out in the selection of suitable material for the manufacture of bolts and product housings.

Phenomenon "bolt" connectors is this today, at a price 5-6 times higher than the price of analogues for pressure testing and with an obviously superior quality of connection by pressing over "bolts" fixing — the Russian market of "bolt" connectors continues to develop .

It is curious that the market is not growing at the expense of the rich, who are not sensitive to the price of consumers, as is the case with the latest models of prestigious and super expensive cars, but at the expense of ordinary people, there are mostly normal and regular customers.

Why, in a country where the standard of living is not as high as, say, Germany, and the question of price outweighs the question of quality and reliability, are bolt lugs so widespread? The answer to this question is rooted in the misconceptions that have surrounded in-ears and connectors since the beginning.

Misconception #1:

"Bolt-on lugs and sleeves are universal in the sense that they can be used for both aluminum conductor cables and copper cables."

Often, the sources of this misinformation are the manufacturers themselves - due to incompetence or other reasons ... In this case, it is said about a certain "special alloy" from which "bolt" connectors are made and the fact that "this alloy is equally well compatible with copper, as well as with aluminum cable «.

In fact, stud bolts and bushings made of aluminum alloys such as B95, D16T, etc. are produced, which implies using them to connect and terminate only aluminum cables. To give them flexibility status, "bolt" connectors (their bodies and bolts) need at least additional nickel or tin-bismuth electroplating.

Misconception #2:

"Bolt connectors are better, more reliable and of better quality than their crimped counterparts, because their price speaks volumes for that."

In fact, the only thing that is proven by the price of "bolt" connectors means higher production costs.

Compared to crimp counterparts:

• "bolt" connectors are actually more massive, which affects the raw material component of the cost;

• during the production of «bolts» more than 50% (!) of the material goes to waste (for «crimping» this value does not exceed 18%).

• Technologically, the production of "bolts" is more labor-intensive and takes a lot of time.

Misconception #3:

« Fastened connectors are better, more reliable and of better quality than their crimping counterparts, as their sturdiness speaks volumes for this, personal, high-tech appearance «.

In fact, a comparative look at "bolt" connectors and their crimp counterparts, it's hard not to agree with the fact that, for example, a "bolt" connector sleeve looks orders of magnitude "cooler" and "more complex" than an aluminum crimp sleeve which is simply a piece of aluminum tubing.

In fact, "cooler" in appearance does not always mean "cooler" in substance.

And the solid and massive appearance of the «bolt» connectors is not at all the desire to make the product look "presentable", there are reasons for this, dictated by constructive necessity.

First, since one model of «bolt» connectors designed to cover the entire range of cable cross-sections (for example, a standard size 70/120 implies installation on a cable with a cross-section of 70 mm², 95 mm² and 120 mm²) - it is manufactured according to the maximum cross-section cross-section (in our case — 120 mm²), and the contact, depending on the installed section, provided by the depth of insertion of the bolt to the tightening of the core.

Secondly, «bolt» connectors, as a rule, originally designed for use with both round and sector aluminum conductors of the cable, which initially required a larger internal diameter of the handle than in crimp terminals, where the sector cores must be pre-rounded using special dies or use a tip one size higher than the cable cross-section.

Third, the thickness of the upper barrel of the «bolts», the tip or the body of the sleeve «bolt» reaches 8 mm (!). Such a shortening is structurally justified by the fact that in this part there are threaded holes for shear bolts. If you make the wall thinner, when screwing in, the bolt will tear off the thread of the connector body earlier than reaching a certain tightening force.

Misconception #4:

"Bolt" connectors install faster than their crimp counterparts. «

In fact, this can only appear to a beginner who has never edited either "live" and has a purely "speculative" view of the process.

professionals

Cons

one standard tip or sleeve size — for the range of cable cross-sections; What corresponds to a similar situation in heat-shrinkable connectors — one connector (set of heat-shrinkable) for a number of cable cross-sections.
no professional tool required: just have standard spanners and a wrench handy.

high cost compared to crimping tips and sleeves;
the mechanical and electrical strength of the contact connection in the case of bolted lugs is significantly lower than crimping;
the risk of breaking the head when the force is less than nominal.

So, despite all the "pluses", the bolts have not displaced traditional lugs and bushings from the market of accessories for crimping cables. This was partly influenced by their "cons". "Bolt", in view of their "weight" (in terms of real weight and price), took its own niche in the market. A matter of taste "…